Yemen’s rebels, known as Houthis, later said in an official statement that they had fired a Scud missile at Saudi Arabia, in what would be the second such attack since fighting between a Saudi-led coalition and the rebels began in the spring.

The security officials, close to the Houthis, said the blast in Sanaa targeted the homes of several Houthi leaders, but did not give further details on how many people were killed or wounded. Houthis cordoned off the area after the explosion and prevented anyone from entering as ambulances rushed to the scene.

The Islamic State’s Sanaa Division claimed responsibility on Twitter for detonating a parked car bomb near the military hospital, according to the SITE Intelligence Group monitoring service.

The fighting in Yemen pits the Shiite Houthi rebels and allied troops loyal to former President Ali Abdullah Saleh against southern separatists, local and tribal militias, Sunni Islamic militants and loyalists of the exiled president. The rebels seized the capital in September. In March, a Saudi-led and U.S.-backed coalition began launching airstrikes against the rebel forces.

Fighting continued in cities across the country on Monday, with Saudi-led airstrikes on the Houthi stronghold of Saada, as well as Aden and Shabwa. In Aden and Taiz, street fighting raged on with heavy weapons, according to security officials who have not declared allegiance to any side in the conflict.

In Shabwa province, tribal leaders and Houthi officials say gunmen attacked a motorcade carrying the Houthi provincial governor and a pro-Houthi military commander, wounding both of them.

All of the security officials spoke on condition of anonymity because they were not authorized to brief journalists.